1. Field of the Invention
The present invention relates to a rewritable recording medium, and more particularly, to a method, apparatus, and computer readable medium for erasing information recorded on a recording medium, and a medium resulting therefrom.
2. Description of the Related Art
In the field for optical recording media, the rewritable digital versatile disc (DVD) market has recently been developing, after the release of read-only DVDs. The rewritable DVDs include a DVD-recordable (DVD-R), which is a write-once disc, and multiple-times rewritable discs such as a DVD-random access memory (RAM), a DVD-rewritable (DVD-RW), and another DVD-rewritable (DVD+RW), for example.
All of the DVD-RAM, DVD+RW, and DVD-RW have recording films formed with phase-change films. The phase-change film has a crystalline structure or amorphous structure based on an applied temperature. By controlling the power of a laser beam appropriately, to form the crystalline structure or amorphous structure of the recording film, information can be recorded. Generally, an area formed with an amorphous structure becomes a mark and an area formed with a crystalline structure becomes a space. The mark and space correspond with digital “1's” and “0's”, respectively.
In the DVD-RAM, when predetermined information is already recorded in at least part of an interval of the disc and another information item is desired to be recorded, the other information item is recorded by writing over the already recorded information without first erasing the already recorded information. Also in the DVD-RW and a DVD+RW, a direct overwrite (DOW) system is employed and new information is recorded in one step for overwriting, without first erasing, already recorded information.
According to the overwrite method, an existing mark is erased and changed into a space, an existing space is changed into a mark, or both existing mark and space are changed into spaces or into marks. However, this overwrite method accelerates deterioration of a recording film and gradually degrades the recording characteristic of the film.
Meanwhile, the DVD-RW defines an erase mode and blank mode in which already recorded information can be erased by a DC erase power level, i.e., a maintained erase power level. The DC erase power level is typically lower than a recording power level, e.g., with there usually being three power levels, a recording power level, the erase power level, and a reading power level. For example, to record to the DVD-RW, the power level an incident light beam must be at least the recording power level. However, when information is recorded after erasing all information recorded on a user data area in the DC erase mode, if the frequency of erasure exceeds about 300 times, the recording characteristic becomes markedly degraded. In the blank mode, information recorded in a user data area of a disc is all erased to make the space empty. A recording medium should guarantee the recording quality of generally over 1000 times recording. However, even though information is erased in the erase mode/blank mode and then recorded in the DVD-RW, if the frequency of recording exceeds about 300 times, the recording characteristic of the DVD-RW is actually degraded such that it is difficult to guarantee usable life and recording quality of the DVD-RW.